I would not consider No. 1 a bug. I suppose the Ceiling Accessory needs a Zone with some height, and this is why it doesn't work in that case.
Can you show a screenshot of No. 2?
Maybe the settings Dialog and also the result in 3D.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28